Here are a couple of vertical measurements. I only took measurements above the tweeter axis since you would need to lie on the floor or turn them upside down to be below the tweeter.
@ugly_woofer said:
The impedance stays above five ohms, but the phase does go heavily negative around 30hz, fortunately it's about twelve ohms there
I've built some speakers with some pretty wonky impedance/phase swings and never noticed anything weird. My personal opinion is focusing on that aspect is a remnant from the tube days.
On the other hand, modern Class D amps can be sensitive to impedance on the top end, so...
I'm always careful about that, but I generally find that if the phase is heavily negative, the impedance at that point is high, but definitely something to pay attention to.
I also agree with JR, that the wild impedance swings don't seem to affect the sound, and I have gone to length s correcting them with no sonic difference.
I could bring my big SET amp so we could hear if there is a big/any difference with and without the Z comp circuit. My single ended, triode strapped, no feedback tube amp would be the most sensitive to impedance swings...
I got the impedance fairly flat it mostly runs between 5 and 6 ohms with a couple of dips into 4.5ish range and the phase is also closer to being a straight line.
That's with the impedance compensation, it doesn't sound any different with my solid state amps, but we will see what happens with Craig's SET tube amp.
I just finished the impedance compensation test jig for Iowa. It's shitty, but functional, it adds or removes the compensation by connecting or disconnecting the banana jumper, so change time is just a second or two.
I am really looking forward to hearing this w/wo imp comp comparison with my tube amp. I am guessing there will be an audible difference, just don't know how much there will be.__
I read a lot of hard claims on the old WWW and some of them aren't true in my experience. For example: I never put a resistor in series with a bottomless tank (ie small cap across a woofer's inductor) because it __might_cause an amp to be unstable at high frequencies. None of my amps have ever broken out into oscillation._
Even so, the possibility is present. The other way is a resistor in the shunt tied to the 2nd order cap. It's only a quasi-short/capacitive load at ultrasonic frequencies though. Since most of what music is, is NOT this range frequencies, it's likely that just a bad amplifier design will have issues with it. It's also likely that such a design is borderline unstable to start with.
I have done some resistorless tanks myself, and my Crowns and older Technics receiver did not seem to care either.
If we are to be truthful and provide all necessary information, then this possibility should be mentioned.
Comments
I'm totally Buff!
My back hurts just thinking about moving those beasts across a room! Will they have carpet sliders instead of spikes? Maybe locking casters!
I'm really not looking forward to putting these into or getting them out of the trunk for Iowa.
Nick, a bag of cement IS NOT the same as polyfill.
Oh shit, they're not interchangeable? .....but they both come in a bag.
Here are a couple of vertical measurements. I only took measurements above the tweeter axis since you would need to lie on the floor or turn them upside down to be below the tweeter.
10 degrees above the tweeter
5 degrees in black, 10 degrees in red
I only posted this so that you guy's can see the trend.
The impedance stays above five ohms, but the phase does go heavily negative around 30hz, fortunately it's about twelve ohms there
I've built some speakers with some pretty wonky impedance/phase swings and never noticed anything weird. My personal opinion is focusing on that aspect is a remnant from the tube days.
On the other hand, modern Class D amps can be sensitive to impedance on the top end, so...
Rod Elliot has an excellent article on the dangers of high phase angles and low impedance: https://sound-au.com/patd.htm.
I'm always careful about that, but I generally find that if the phase is heavily negative, the impedance at that point is high, but definitely something to pay attention to.
I also agree with JR, that the wild impedance swings don't seem to affect the sound, and I have gone to length s correcting them with no sonic difference.
I always thought wild impedance swing were because I used to many parts
Or cheap capacitors
It's possible to flatten the impedance, but it requires, wait for it.............OH GASP!!!.... more parts. lol
Impedance sim
Pancaked
Required circuit
Life is a bit complicated right now, but if I get some time, I'll throw this together, test it and post the results.
Just put them (crane?) into the car and drive down I-80, we can have Samson test them next Saturday
Done! I'll be there Friday night.
I could bring my big SET amp so we could hear if there is a big/any difference with and without the Z comp circuit. My single ended, triode strapped, no feedback tube amp would be the most sensitive to impedance swings...
That sounds like a great idea Craig,. My amps don't seem to care much, but a tube amp with a high out impedance could very well show a difference.
Ok, I'll bring it.
I got the impedance fairly flat it mostly runs between 5 and 6 ohms with a couple of dips into 4.5ish range and the phase is also closer to being a straight line.
Holy $hit. Mine never look look like that.
That's with the impedance compensation, it doesn't sound any different with my solid state amps, but we will see what happens with Craig's SET tube amp.
Wow, I'm surprised the sound didn't change - especially in the top end.
I just finished the impedance compensation test jig for Iowa. It's shitty, but functional, it adds or removes the compensation by connecting or disconnecting the banana jumper, so change time is just a second or two.
Now that's what I call an inductor! Over a pound of metal just in that one part.
The inductor was purchased specifically for this application!!!! Nah, it was just in my parts inventory and happened to be what I needed.
You must have a big parts bin!
I am really looking forward to hearing this w/wo imp comp comparison with my tube amp. I am guessing there will be an audible difference, just don't know how much there will be.__
I read a lot of hard claims on the old WWW and some of them aren't true in my experience. For example: I never put a resistor in series with a bottomless tank (ie small cap across a woofer's inductor) because it __might_cause an amp to be unstable at high frequencies. None of my amps have ever broken out into oscillation._
Even so, the possibility is present. The other way is a resistor in the shunt tied to the 2nd order cap. It's only a quasi-short/capacitive load at ultrasonic frequencies though. Since most of what music is, is NOT this range frequencies, it's likely that just a bad amplifier design will have issues with it. It's also likely that such a design is borderline unstable to start with.
I have done some resistorless tanks myself, and my Crowns and older Technics receiver did not seem to care either.
If we are to be truthful and provide all necessary information, then this possibility should be mentioned.
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